This invention relates to a workpiece manipulator which can be applied to the hand of a robot, and more particularly to a workpiece manipulator which has two fingers and which is adapted such that the point toward which the fingers approach in gripping a workpiece will always be at the same fixed position located exactly midway between the fingers.
Industrial robots are equipped with a hand for carrying a workpiece to a prescribed location. For this purpose a workpiece manipulator having fingers for gripping the workpiece is provided at the end of the hand. In repeatedly gripping and carrying a number of workpieces of the same diameter it is possible to stabilize the gripping operation by arranging it such that the fingers of the workpiece manipulator approach the same fixed position midway between the fingers each time a workpiece is gripped. In general this is accomplished by connecting the fingers of the manipulator such that they will be displaced mechanically by equivalent amounts. For example, one such method makes use of a screw rod which is threaded from the center thereof in opposing directions, that is, to the left and right. Drive portions for each of the fingers are engaged with respective ones of the oppositely directed threaded portions of the rod so that, when the rod is rotated, the two fingers are caused to approach or separate from each other thereby to grip or release a workpiece. However, one disadvantage encountered with this method is the high cost necessitated by the fairly complex mechanism that transmits the rotating motion to the screw rod.
Another method which offers a simpler construction proposes the use of a pantagraph-type lever mechanism. In this case, however, it is difficult to make the fingers approach the same fixed position for each operation thereof because of play or backlash which develops in the connecting portion between levers.